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5069731 
Journal Article 
Ultrasmall Cobalt Nanoparticles as a Catalyst for PET Glycolysis: A Green Protocol for Pure Hydroxyethyl Terephthalate Precipitation without Water 
Veregue, FR; Pereira da Silva, CT; Moises, MP; Meneguin, JG; Guilherme, MR; Arroyo, PA; Favaro, SL; Radovanovic, E; Girotto, EM; Rinaldi, AW 
2018 
6 
9 
12017-12024 
WOS:000443924100100 
Polyethylene terephthalate (PET) is a very stable polymer widely used in the modern world. Due to its stability, this polymer can remain in the environment for several years before its complete degradation. The glycolysis reaction of PET has emerged as a green approach to obtain the PET monomer, thus avoiding such environmental problems and adding value to this waste. In this work, PET waste was depolymerized by glycolysis using ultrasmall cobalt nanoparticles (1.5 wt %) as the catalyst for the production of bis-2-hydroxyethyl terephthalate (BHET). A capping agent (tannic acid, TA) and a borohydride reduction approach were used to obtain such ultrasmall cobalt nanoparticles (similar to 3 nm). A PET depolymerization yield of 96% was achieved within 3 h at 180 degrees C. The precipitation of 77% of pure BHET was achieved without the need for water. The remaining ethylene glycol solution containing the ultrasmall cobalt nanoparticle catalyst was reused five times for this glycolysis process, demonstrating the feasibility of solvent reuse without the need for any treatment. A reaction mechanism is proposed in order to explain the high BHET yield obtained by this ultrasmall cobalt nanoparticle catalyst stabilized with TA. 
Borohydride reduction; Depolymerization; Glycolysis reaction; PET recycling; Reusability; Ultrasmall nanoparticles